First of all, it is worth noting that the first genetically modified (GM) product approved by the FDA was insulin, produced by modified bacteria. GMOs were also developed to improve crop characteristics either by accelerating the introduction of a better version of existing genes into a crop or by enabling the introduction of completely new genes to provide new properties.
There are four main objectives:
First, genetically modified (GM) plants are used as a quick way to prove that a gene that is supposed to provide a new characteristic to a plant is actually doing the job.
Let’s say a scientist thinks a gene located on a chromosome in a plant is potentially providing resistance to a fungus. To be sure that the gene is really responsible for the resistance, the scientist will introduce this gene in a variety that is susceptible to the fungus. If the variety becomes resistant, then he/she knows that the gene is a resistance gene, and he/she can use it further to improve resistance of a crop to this fungus in the field. Thus, GMOs are useful to better generate knowledge, i.e. understand how plants work and survive in their environments.
Second, genetic modification offers the possibility to accelerate the introduction of a gene to provide a better characteristic (better resistance to a disease, better yield, better tolerance to drought, etc.) into a crop compared to classical breeding.
While it takes 15 years to introduce a new gene into a variety and combine it with other desired characteristics through classical breeding, it technically takes less than seven years to do the same using a GM approach (that is without counting the time for deregulations).
Third, genetic modification enables crops to acquire completely new functions that are otherwise brought by the use of natural or synthetic chemicals.
For example, many crops do not have genes that naturally protect them against insects eating their leaves or roots. In contrast, there are a lot of soil bacteria or fungi that carry this type of genes naturally. Thus, if a scientist discovers such a gene in a bacteria, and introduces it into a plant, thereby creating a GMO, the plant can now produce its own insecticide. By doing this, fewer chemicals are required to be sprayed in the fields to kill the insects.
Finally, GMOs can be produced to protect a crop against an herbicide that is used to control weeds.
By introducing a new gene or modifying the function of an existing gene into a crop, GM technologies provide herbicide tolerance to crops. Therefore, it becomes possible to control weeds in the fields without affecting the crop yield.